A solar thermal power plant based on Direct Steam Central Receiver (DSCR) includes a large field of heliostats and a solar receiver placed on a tower of substantial height. The heliostats focus direct sunlight on to the solar receiver to produce steam to be utilized to run a steam turbine from producing electricity. Typically, the solar thermal power plant operates on a daily cycle, during clear sunlight hours, while shutting down in nights or in cloudy weather. However, if the solar thermal power plant is to meet increasing electricity demand, it needs to be operable irrespective of the availability of solar radiation, i.e. in nights or in cloudy weather. A realization of such a solar thermal power plant generates a requirement of storing solar thermal energy during day times and utilizing thereto in nights or in cloudy seasons. For such requirement, a central receiver including a solar energy storage fluid, such as molten salt, is generally used. The central receiver with molten salt is generally known as Molten Salt Central Receiver (MSCR).
In a typical MSCR system a MSCR, hot and cold storage tanks and a Molten Salt Steam Generator (MSSG) cycle are arranged to utilize the solar energy to produce electricity. In such arrangement, the molten salt fluid heated at the MSCR is stored in the hot storage tank, at temperature of about 565° C., and after thermal energy thereof is being utilized by the MSSG cycle, it is stored in the cold storage tank, at temperature of about 290° C., from where it is further sent to the MSCR to be reheated. In such arrangement, during day and night both, the hot molten salt is pumped through the MSSG cycle to produce steam, which is utilized to produce electricity.
During night, such utilization of the stored molten salt from the hot storage tank by the MSSG cycle using pumps may be effective, however during daytimes, when both of the MSCR and MSSG are working at the same time then such pumps adds significant auxiliary power consumption and reduce overall efficiency of the power plant. The efficiency of the plant may be improved by extracting work from the molten salt that is flowing from the MSCR kept at the height, having sufficient pressure to utilize for generating power or to drive auxiliary equipment and reduce auxiliary power consumption.